Emergency contraception has the ability to prevent pregnancy after unprotected sex or when normal contraceptive methods fail. Utilizing this method does not interfere with birth control pills. On the other hand, birth control pills are more effective than emergency contraception (when properly used) and there is no additive effect.
The "morning after" pill is a form of emergency contraception. This medication can be used to prevent pregnancy up to 72 hours after unprotected sex. When used properly, the morning after pill is 80 percent effective at preventing pregnancy. This means that four out of five women who would have become pregnant do not become pregnant.
The morning after pill can come in one of two formulations. One type of emergency contraception pill just has one hormone, Levonorgestrel. Others combine two hormones, progestin and estrogen. Some formulations require you to only take one dose to be effective, but others require two separate pills to be taken.
The emergency contraceptive pills work because pregnancy rarely (if ever) occurs immediately after unprotected sex. Instead, the woman must ovulate (produce a viable egg) and then, even once the egg has been fertilized, it must plant itself in the uterus. Morning after pills work by preventing ovulation and by preventing fertilized eggs from implanting themselves in the uterus.
Emergency Contraception and Birth Control Pills
Emergency contraception pills do not interfere with oral contraceptives. In fact, some kinds of birth control pills can be taken in high doses for emergency contraception. On the other hand, birth control pills and the morning after pill work via the same mechanism, so the only reason why both would be indicated is if the woman had missed two or more consecutive days of birth control pills. In that case, the woman would need to start a new cycle of birth control pills anyway.
Taking an emergency contraception medication can cause nausea and vomiting, especially if taken with birth control pills. Other side effects include menstrual changes, potentially causing the next menstrual period to be irregular. The morning after pill can also cause fatigue, a headache and abdominal pain.